Many semi-trailers used for merchandise transport have a rear roll-up door. Such doors customarily have rollers and hinged horizontal panels that fold as the door is opened by being slid customarily in an upward direction with the rollers in glides that typically curve inward at the top of the trailer at an angle approximately ninety degrees. Various locking devices have been proposed to secure roll-up doors against thieves who use bolt cutters, power hack saws, and sledge hammers to destruct the latch and/or the padlock securing the latch. The doors are traditionally secured by a J-hook pivotally mounted on the door near its bottom end. Rotation of the J-hook in a clockwise direction engages the claw of the J-hook with a fixed structural component in a rear transverse bumper, a portion of which extends rearward of the door. The operating lever of the J-hook is usually further secured by a padlock with its shackle extending through openings in the operating lever and a pivoted a lever latch a stop block fixed to the door. One J-hook manufacturer provides a lever stop having an opening through which the shackle also extends when the lock secures the J-hook lever. There are basically two styles of J-hooks for securing roll-up doors in the industry, which are named after the principal manufacturers. Most other manufacturers use a design of one of the primary two. Prior art regarding lock guards is replete with a myriad of diverse and specialized lock guards. Particularly relating to roll-up doors are Eberly U.S. Pat. No. 4,895,077 and Sole et al. U.S. Pat. No. 5,737,946. Whereas both Eberly and Sole teach the use of lock guards to protect padlocks securing the locking mechanism on roll-up doors, both applications are designed to function on only one of the two primary locking handle manufacturers and their designs will not allow universal applicability. While all of the aforementioned prior art constructions are more than adequate for the basic purpose and function for which they have been specifically designed, none of these patented devises have been specifically designed to transcend the nuances of difference between the two primary manufacturers such that one common lock guard can transcend the difference.